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Identifying Track Makers By Scarlett Hunt The importance of fossil trackways to palaeontology is noted in this quote from Lockley &amp; Hunt:

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“Every tetrapod animal can potentially make hundreds of thousands, even millions, of tracks in a lifetime, whereas it only has one skeleton consisting of a few hundred bones.”

Palaeontologists try to glean as much information as possible from dinosaur tracks. They can examine the patterns, spacing, size, shape and depth of prints. They take into account the site’s palaeoecology and biostratigraphy and the many variables which affected the formation of the print. Paleontologists then use this information to speculate about dinosaur anatomy, posture, locomotion, speed and behaviour. By piecing together these clues from the past, paleontologists hope to identify trackmakers and better understand their anatomy and behaviour.

The front foot of a quadruped animal is called the manus, whereas the back foot is called the pes.

In Clayton Lake State Park, Oklahoma approximately 500 footprints of iguanodonts are remarkably preserved . The three-toed footprints indicate that the animal usually walked bipedally but occasionally leaned forward to walk on all fours. The tracks are easily recognized because of their square heels and lack of claw marks.

A pattern of distinct foreprints and hindprints indicates that the animal was an obligate quadruped; it walked only on four legs. The pattern may show the foreprints alternating with the larger hindprints or the foreprints may be embedded inside the larger hindprints (as “underprints”).

When there is a pattern of hindprints and foreprints with a few foreprints missing, the animal is a facultative quadruped who was capable of walking on two legs but usually did not.

Chart and information taken from: “An Overview of Dinosaur Tracking” by Glen Kuban

According to the author of www.palaeo.gly.bris.ac.uk /Palaeofiles/Tracks/Report9, “The stature and build of the legs and feet will affect the area over which pressure is exerted. Wider feet will have a “snowshoe” effect and therefore leave less of an impression. Column-like legs with compact feet will carry the mass of the body over a smaller area. This will exert a high pressure and produce a more profound disturbance of the substrate.”

The soft tissue of an animal’s foot can greatly affect the shape of a print. It can be entirely different from what you would expect to find based on the skeleton alone. For example, Robert Bakker speculated that duckbilled hadrosaurs had plump paws similar to a camel’s foot. This would produce a webbed footprint.

PROBLEM: One mystery is why the front prints show only blunt digits marks, whereas skeletal remains of sauropod front feet include a large pointed claw. Glenn Kuban speculates that perhaps the single claw was held in an elevated position or else the claw was tucked within the fleshy pad at the front of the foot.

Scientists use Roman Numerals to count fingers and toes. They are numbered from the inside to the outside. For example your thumb would be “I” and baby finger would be “V”.

When counting phalanges (bones) in the digits, they are numbered from the palm of the hand outward.

Small Allosaurus Hand

Small Raptor Foot

Each finger or toe is also part of a phalangeal formula for the hand or foot. For example a human hand is “2,3,3,3,3” because the thumb has 2 bones and each other finger has 3. A theropod foot has the formula “3,4,5”.

Ankylosaur and ceratopsian footprints each have 4 digits on the back feet and 5 on the front feet.

Most bipedal dinosaurs actually possessed 4 digits on each foot, but one digit (the hallux) was small and held in an elevated position at the inside rear of the foot. When recorded at all, hallux marks are usually small and shallow.

However, one of the problems is that foot bones are small and hard to find. Often trackways are given their own names because the animal is known only by its footprints; these are called ichnofauna. The name of the animal and the name of the trackway it made may be different.

Dilophasaurus is however very unusual in that its skeletons have been found in relatively close proximity to footprints plausibly made by the dinosaur.

Hadrosaurs are probably the best known ornithopods that left tracks attributable to the trackmaker.

“The only way to demonstrate conclusively that any one species of dinosaur was responsible for a particular type of footprint is to discover the skeleton of the animal preserved at the end of its fossil trackway.” (Thulborn, 1990).

Dinosaurs with tridactyl feet tended to produce three-toed footprints, those with slender feet tended to produce narrow footprints, and so on. In other words, it may be assumed that each footprint is a reasonably faithful impression of the foot that made it. The obvious way to discover which sort of dinosaur was responsible for a trackway is simply to match up the footprints with dinosaur feet of the most appropriate shape and size. Such matching up of dinosaur footprints against dinosaur feet has long been standard practice (see diagram).

Sometimes the fossil footprint is compared directly to an actual foot skeleton; alternatively, one may work from the evidence of the footprint alone, attempting to visualize the shape of the foot that might have produced it. On occasion, it is useful to follow the reverse procedure, by predicting what sort of footprint would be produced by a particular foot skeleton. This last exercise entails something more than laying out the foot bones on a sheet of paper and tracing round them with a pencil. Instead it is necessary to arrange (or at least envisage) the foot bones in a life-like attitude, with the bases of the digits lifted from the substrate and the metapodium inclined up and backwards. Then, when they are projected on to the horizontal plane, these inclined elements will appear properly foreshortened, as they would be in an actual footprint.

Indirect information can be interpreted from the tracks in-situ. Palaeontologists speculate about the movement of individuals or groups, social behaviour related to grouping, action sequences, distribution of groups, populations, ecology and food chain, relative ages of individuals in the group, etc.

Eubrontes giganteus tracks is at Dinosaur State Park in Rocky Hill, CT

Paleontologists may estimate an animal’s speed by combining factors into an equation determined by R. McNeil Alexander in 1976.

V=

Alexander estimated from a range of dinosaur skeletons that the hip height ranged from 3.6 to 4.3 times the foot length. “The hip height equals 4 times the foot print length” has become widely used as a convenient and easily remembered rule of thumb.

Using Alexander’s equation, the follow speeds were calculated by R. A. Thulborn (1982, University of Queensland, Australia):

In the Paluxy riverbed of Glen Rose, Texas, palaeontologists claim to have found evidence of an action sequence frozen in time. Roland Bird and crew examined a large set of sauropod trackways. They discovered that a set of large carnosaur tracks parallels the sauropod tracks. This lead Bird and others to speculate that they record an ancient chase scene.

Other critics point out that the paces are rather small and show unhurried gaits. They concede that the carnosaur may have been stalking the sauropods from a distance, or more likely was simply using the same path at a different time.

Because of the regular spacing of tracks of the same type of animal many believe that these tracks are the oldest evidence of herding behaviour in animals. They suggest that the tracks indicate a “follow the leader” pattern of movement.

In Brule, Nova Scotia palaeontologists have found evidence of a primitive conifer forest ecosystem from the Permian Period (285 MA). Animal tracks meander along the forest floor between fossilized Walchia stumps found in their original growth positions.

The reptilomorph called Seymouria dragged its tail as it walked. Remarkably the Brule trackway shows that the tail drag was raised in narrow areas between trees.

Amphibian trackways in the cliffs near Diligent River, Nova Scotia have preserved evidence of the palaeoenvironment. There are five remarkable sets of footprints, three with tail and body drags. Fern stems and fronds, load casts, tree rootlets, drag marks and rain drop impacts were also preserved on the surface of the rocks.

In “A Study of Small Dinosaur Footprints-Gary Gaulin challenges the view that ornithischian dinosaurs were strictly herbivores. He examined a site which contained insect trails along Anomoepus scambus trackways. Notably there was no preserved evidence of vegetation. He theorizes that these small dinosaurs fed on small insects.

In “An Overview of Dinosaur Tracking” Kuban states that “When a track is made on very soft substrate, some sediment may slump back into the print. This phenomenon, called mud-collapse or mud back-flow, often distorts and reduces track features. Digit marks may become mere slits. Soft sediment can also result in undertracks. If the substrate is very firm, portions of the foot may record only lightly, if at all.”

Tracks in Courtedoux, Switzerlandof at least 14 sauropods and two tracks of a carnivor.

In small and poorly preserved tracks it is difficult to distinguish between ornithopod and theropod tracks. For example, small carnosaur species or juveniles of a carnosaur species may make tracks mistaken for large ornithopod tracks when their digits are partially mud-collapsed. This would make them appear to be shorter and blunter and therefore more ornithopod-like.

A three-dimensional computer reconstruction (top) shows a theropod foot at three stages in creation of a deep track, moving right to left. A photograph of a deep Greenlandic footprint is shown below it.Image: Stephen Gatesy, Brown University

“Increasing speed will alter the angle at which the foot contacts the ground and affect the force with which the foot strikes the substrate…

A foot print is usually made in three phases, termed touch-down, weight-bearing and kick-off. (Thulborn & Wade, 1989).

Many animals perform a small rotation of their feet during the progress of a footfall (Phil L. Manning, pers.comm.). This rotation, within the print, will naturally obscure some of the finer details of the foot structure. However, if recognized it may tell us a great deal about the trackmaker’s locomotion.”

This three-dimensional computer image reconstructs theropod foot movements through sloppy mud. Penetration through the ground surface is shown in red. The first toe, which is not reversed as in modern birds, creates a rearward pointing furrow (a,b) as it plunges down and forward. The sole of the foot leaves an impression at the back of the track (c) because it is not lifted as the foot sinks. All toes converge below the surface and emerge together from the front of the track (d). Image: Stephen Gatesy, Brown University

Undertracks can occur when tracks are made upon other previously laid tracks.

Rock change may destroy evidence of tracks.

A hiatus is a geological period of time without deposition containing fossils. No trackways are formed.

Paleontologists will continue to painstakingly examine evidence from the past in order to reconstruct and describe it for others. They will skillfully examine direct evidence, make interpretations, consider the affects of variables, and may encounter monumental problems along the way. In the future we may see more importance placed upon Ichnology (the study of trace fossils) and on the identification of species from their tracks.